The present invention relates to the application of solar heat for heating swimming pools, houses, domestic water supplies, etc. There have been many systems proposed for utilizing solar heat for heating swimming pools. Most of them are not commercially feasible because of their high cost or lack of efficiency. Many are limited in application because of a lack of ability to retain pressure. Others do not have the capability of being operated as a closed system as well as an open system. Some do not have the structural rigidity to support themselves while others are so rigid that they cannot be favorably disposed to capture the sun's radiation in the most efficient manner. What is needed is a highly efficient, inexpensive, versatile system which can compete with other forms of energy in an economic and reliable way. This invention addresses itself to all of these problems.